1. Field of the Invention
The present invention relates to a light-sensitive material. More particularly, the present invention is concerned with a sensitized light-sensitive material containing at least one organic compound which contains tellurium or selenium.
2. Description of the Prior Art
Although silver halide light-sensitive materials are preferred photographic materials due to their high sensitivity, these materials suffer from the drawbacks that complicated liquid treatments are required for the formation of photographic images after image-wise exposure, which require skill of a high degree and long periods of time, and these materials are high priced since silver is used as a starting material.
Light-sensitive materials per se for use in diazo photography (in which diazonium compounds are used) are cheap as compared to silver halide light-sensitive materials. With diazo light-sensitive materials, however, developing processing using an alkali bath is generally required. Even in the case of thermal diazo photography (dry system) where solution treatments as described are not required, alkali generating agents must be incorporated in the light-sensitive materials. In the case of the Kalvar process in which diazonium compounds are used, a colored image cannot be obtained even if dry processing systems are used, and thus only photographic films for projection are obtained.
With photographic light-sensitive materials using light-sensitive polymers, a liquid treatment is necessary, and, furthermore, as in the case of the above Kalvar process, a colored image cannot be obtained.
Moreover, in the case of free radical photography, dry processings are usually used. However, disadvantages are sublimation, toxicity and low stability of the starting materials, and, furthermore, the images formed are often unstable due to difficulty in fixing the images.
Certain light-sensitive materials have considerably improved these defects of conventional photographic light-sensitive materials, for example, those light-sensitive materials wherein metal salts of organic acids such as behenic acid salts are used as image-forming materials in combination, with silver halide as a light catalyst and a reducing agent. Such materials are marketed under the tradename "Dry Silver", and can be produced by the techniques as described in Japanese Patent Publications 2096/1963, 4921/1968 and 4924/1949.
Such light-sensitive materials, however, are expensive due to the use of silver as an image-forming material. Furthermore, their storage stability prior to use is often poor, and it is necessary to use toxic silver compounds to prevent the formation of fog at thermal development.
In place of the above light-sensitive materials, an image-forming method in which tellurium or selenium-containing organic compounds are used is described in Japanese Patent application (OPI) 29438/1973, Japanese Patent Application 14330/1974, etc. In such a method, an organic compound containing tellurium, or selenium, in some cases in contact with a light sensitizing agent, and a binder are coated on a support. On exposure of the member so produced to light followed by development by heating, an image is formed due to the contrast of the tellurium or selenium.
With such light-sensitive materials, photographic sensitivity can be increased to a certain extend by adding a light sensitizing agent. Up to now, however, sufficient sensitivity has not been obtained, and thus more effective sensitizing techniques have been desired.